The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk (such as a magnetic disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly includes at least one head, typically several, for reading and writing data from and to the disk. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, and at least one head gimbal assembly with a flexure. A conventional “rotary” or “swing-type” actuator assembly typically includes a rotary actuator having an actuator body. The actuator body has a pivot bearing cartridge to facilitate rotational movement of the actuator assembly. An actuator coil is supported by the actuator body and is configured to interact with one or more magnets, typically a pair, to form a voice coil motor. One or more actuator arms extend from an opposite side of the actuator body.
The spindle motor typically includes a rotatable spindle motor hub, a magnet attached to the spindle motor hub, and a stator. The stator typically includes a series of coils that are in electrical communication with the printed circuit board assembly. With this general configuration, the various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the magnet, thereby imparting a rotational motion onto the spindle motor hub. Rotation of the spindle motor hub results in the rotation of the attached disks.
During operation of the disk drive, the heads must be controllably positioned in relation to tracks of the disks. The pivoting motion of the rotary actuator provides a basic mode of actuation of positioning the heads. Prior art attempts have been directed towards providing a secondary actuation of the heads, for example to increase bandwidth or track-following resolution. Such a configuration has been referred to a dual-stage actuation or microactuation. It is contemplated actuation of microactuators may result in vibrational excitation of the associated actuator arms. This is due to the reaction force between the microactuator and a distal end of the associated actuator arm. Such vibrational excitation may give rise to an undesirable change in the resonance response of the head stack assembly. This can result in a narrowing of the servo bandwidth to act to deteriorate the function of the secondary actuation of the microactuators. Therefore, it is contemplated that there is a need in the art for an improved microactuator configuration.